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about structure and function

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  1. 1. Aquaporins Aditya(09026) 5th Year BS-MS IISER BHOPAL
  2. 2. What is Aquaporin ?? • Aquaporin is a 28 kDa protein embedded in the cell membrane in order to regulate the flow of water • presence of these water channels increases the permeability to water of the cell membrane • Thousands of millions of water molecules per second pass through one single channel • Found in all kingdoms of life including bacteria, plants, and mammals • 13 in mammals, 6 in kidney • In plants- 4 families
  3. 3. HISTORY • In the mid 1950s-water can pass through some pores • Till early 80s-there are some sort of selective filter that prevents ions from passing through the membrane while water molecules can pass • In the mid-1980s Peter Agre studied various membrane proteins from the red blood cells and also found one of these in the kidney. • Having determined both its peptide sequence and the corresponding DNA sequence, he realised that this must be the protein that so many had sought before him: the cellular
  4. 4. HISTORY.. • In 1992 Peter Agre at John Hopkins University reported his unintentional discovery of aquaporin, he earned a Nobel Prize for his discovery in 2003 . Crystallographic structure of the aquaporin 1 (AQP1) channel (PDB 1J4N)
  5. 5. STRUCTURE • Aquaporin appear to assemble in membranes as homotetramers in which each monomer, consisting of six membrane-spanning α-helical domains with cytoplasmically oriented amino and carboxy termini. • two well-known channel constriction sites in the peptide are NPA motif and a second and usually narrower constriction known as 'selectivity filter' or ar/R selectivity filter.
  6. 6. STRUCTURE.. NPA Motif
  7. 7. STRUCTURE.. ar/R selectivity filter
  8. 8. Importance of Aquaporins • Aquaporin are known to play a big role in various aspects of normal body function. • Many mammalian AQPs, including AQP1, AQP2, AQP4, AQP5 and AQP8, function primarily as bidirectional water-selective transporters. • It is seen that most, if not all, significant biological functions of the mammalian AQPs, can be attributed to AQP facilitated water and/or glycerol transport. • In oocytes it transport glycerol and to some extent urea, along with water.
  9. 9. Diseases • Several diseases such as congenital cataracts and nephrogenic diabetes insipidus are relate to mutations in aquaporins, also fluid transport, brain swelling, strokes, meningities, multiple sclerosis. • A small number of people are found with a deficiency of aquaporins and they generally seem healthy, but they have a defect in the ability to concentrate solutes
  10. 10. THANK YOU !!!
  11. 11. References • Aquaporin water channels: molecular mechanisms for human diseases1-by Peter Agre, David Kozono • Aquaporins at a glance byAlan S. Verkman • ns/ • • 3/october/031008a.htm